Overhead camshaft assembly for internal combustion engines



Nov. 26, 1968 R. BINDER 3,412,720

0'. ..X AD CAMSHAFT ASSEMBLY FOR INTERNAL COMBUSTION ENGINES Filed June 27, 1967 A TTU/Zn/EYS United States Patent 3,412,720 OVERHEAD CAMSHAFT ASSEMBLY FOR INTERNAL COMBUSTION ENGINES Robert Binder, Schwieberdingen, Germany, assignor to Firma Dr.-Ing. l1.c. F. Porsche K.G., Stuttgart-Zulfenhausen, Germany Filed June 27, 1967, Ser. No. 649,346

Claims priority, application Germany, July 7, 1966,

Claims. (Cl. 123-90) ABSTRACT OF THE DISCLOSURE The present disclosure relates to an internal combustion engine, particularly air-cooled, having cylinders arranged in one or more rows, wherein the cylinder heads of one row of cylinders are separate and interconnected by means of a tubular support member or pipe that is preferably made of a single piece extending over the entire length of the cylinder row to serve as a housing and support for the camshaft. Aligned bores are provided in the corresponding cylinder heads for receiving therein the pipe. The internal surface of the pipe is disposed eccentrically with respect to the outer surface to provide room for a lubricating duct in the wall having the largest thickness.

In the prior art, internal combustion engines, particularly those that are air-cooled, have been provided with one or more rows or cylinders and a camshaft arranged overhead in the cylinder head; the cylinder head being of a single piece of construction for all of the cylinders of one row. The reasons of this type of prior art construction has been to provide a relatively stiff and rigid housing for the camshaft. It is also known to provide the cylinders of an air-cooled internal combustion engine with individual cylinder heads and to arrange the camshaft in auxiliary housing secured to the top of cylinder heads by means of a plurality of screws or the like. With this latter construction, the housing bridges as one piece, the cylinders of a row of cylinders of the internal combustion engine. Such a construction has the distinct disadvantage that it requires large tools and machines, and defects that originate during casting or subsequent machining result in large work pieces becoming unuseable. Additionally, the construction of the bridges between the valves, especially for V-arranged valves, cannot be shaped as desired, which is extremely disadvantageous in regard to high-output internal combustion engines.

It is an object of the present invention to avoid the above mentioned disadvantages of the prior art constructions and to provide an internal combustion engine with a plurality of individual cylinder heads and an overhead camshaft While providing a specific structure resulting in considerably less weight.

The invention relates to an internal combustion engine having cylinders arranged in one or a number of rows, with individual cylinder heads associated with each cylinder. The cylinder heads of a row of cylinders are interconnected with each other by means of a pipe or tubular support, which preferably consists of one piece and extends over the entire length of the cylinder row to serve as housing and support for the camshaft.

With the above construction of the present invention, the support for the samshaft is easy to produce and to assemble. Furthermore, it is quite easy to line up the cylinders in a space saving manner, without the necessity of the camshaft support functioning as a cover or cover housing. The pipe or tubular support may be readily and cheaply produced, because of its simply constructed surfaces in contrast to prior art arrangements that have com- Patented Nov. 26, 1968 ice plicated configurations requiring expensive casting and machining. On the basis of equal strength, the support of the present invention is considerably lighter in construction when compared with the prior art devices. The connection of the pipe with each of the cylinder heads is accomplished by means of aligned bores in the cylinder heads to receive therein the pipe in a bearing manner while avoiding a plurality of complicated fastening means. The inner surface of the pipe is eccentric with respect to the outer surface thereof so that the largest thickness walls are relatively reinforced and provided with fastening means for axially and rotationally securing the pipe, for example. Also, a lubricating duct may be provided in the walls of the pipe, preferably the wall having the largest wall thickness. By means of this lubricating duct, individual portions of the camshaft, particularly its bearings, may be provided with lubricating oil in a simple and economical manner.

Further objects, features and advantages of the present invention will become more clear in connection with the following detailed description of the drawing, wherein:

FIGURE 1 is a partial longitudinal cross sectional view taken through an internal combustion engine employing the inventive features of the present invention; and

FIGURE 2 is a cross sectional view taken along line IIII of FIGURE 1, on a reduced scale.

As shown in FIGURE 1, the air-cooled internal combustion engine includes a plurality of individual and separate cylinder heads 1, 2, 3, which are arranged in a single row of cylinders; other individual cylinders in the row and additional rows of cylinders are not shown in the drawing. The cylinder heads 1, 2, 3 are interconnected by means of a pipe or tubular support member 4 that 7 extends as a unitary, preferably single piece, over the entire length of the cylinder row. The back portions of the individual cylinder heads are provided with bores 5, 6, 7, respectively.

Each cylinder head is provided with valves 8, 9, which are actuated by means of rocker levers 10', 11 that are pivoted by suitable cams arranged on the camshaft 12. The rocker levers 10, 11 are supported by bolts 13, 14 having an outer spherical or ball shape for engaging the levers. The bolts 13, 14 are supported in the covers 15, 16, respectively, which provide access to the control members in the cylinder head. The camshaft 12 is supported in the pipe 4 by the internal cylindrical surface 17 of the pipe that directly engages the plurality of cylindrical bearing surfaces of the camshaft, which are of equal diameter. The internal surface 17 is eccentric with respect to the outer cylindrical surface 18 of the pipe 4. In the area 19 having the largest wall thickness of the pipe, a lubricating duct 20 is cut or otherwise formed to be connected to the lubricating oil system, not shown, for supplying lubricating oil through substantially radially extending lubricating passageways 21 to the cams on the camshaft and the supporting bearings. The lubricating duct 20 may also supply hydraulic fluid for operating the adjusting mechanisms 25 that adjust the valve clearance. Such an adjusting mechanism is shown in FIGURE 2 for axially moving the bolt 13 to change the position of the fulcrum point for the rocking lever 10, is shown as mounted in the cover 15. For this purpose, the pipe 4 is provided with cutouts 22 for providing fluid communication between the lubricating duct 20 and a bore 23 in the cylinder head 1. The bore 23 is in fluid communication with a passage 24 in the cover 15 to supply hydraulic fluid to the adjusting mechanism 25, which is of known construction per se.

The pipe 4 is provided with cut out portions or substantially radially extending openings 26, 27, which allow engagement between the rocker levers 10, 11 and the cams on the camshaft 12. These cutouts are also constructed to provide lateral support and guiding for the rocking levers.

Adjacent to the bolts 13, 14 there are provided threaded plugs 28, one being shown with respect to the bolt 14. The threaded plugs 28 close a correspondingly sized opening in the cover 16 through which adjustment of the valve clearance may be performed.

The pipe 4 has an outer cylindrical surface that conforms to the cylindrical surfaces of the bores 5, 6, 7. The pipe 4 is held in the cylinder head 1 by one or more screws 29 to prevent rotation. The camshaft 12 is axially secured by means of an integral shoulder or abutment flange 30 at one axial end. The abutment flange 30 may be integrally formed with a driving gear or chain sprocket 31 for driving the camshaft by means of a chain (not shown) connected to the crankshaft of the internal combustion engine.

The camshaft is axially urged into abuting engagement by means of a spring 32 that engages the end of the camshaft by means of a ball 33, both of which are held and guided within a housing 34 for the control gearing drive.

Although one specific preferred embodiment has been described in detail for purposes of illustration and to provide specific advantages, further modifications, embodiments and variations are contemplated within the spirit and scope of the present invention as defined by the following claims.

I claim:

1. An internal combustion engine, comprising: at least a plurality of engine cylinders arranged in a single longitudinal row; a separate cylinder head for each of said cylinders attached thereto; a tubular support member of unitary construction mounted on said cylinder heads; a camshaft rotatably mounted in said tubular member; means for rotatably driving said camshaft.

2. The engine according to claim 1, including a separate bore in each of said cylinder heads longitudinally aligned with the bores in the other of said cylinder heads and said tubular support member being mounted within said bores.

3. The engine according to claim 2, wherein said tubular support member has an exterior cylindrical surface and an interior cylindrical surface eccentric with respect to said exterior cylindrical surface to provide wall portions of different thickness.

4. The engine according to claim 3, including a longitudinally extending lubricating duct within the wall portions of said tubular support member.

5. The engine according to claim 4, wherein said lubricating duct is located in the wall portion having the largest wall thickness.

6. The engine according to claim 5, wherein said tubular support member has a cylindrical bearing surface extending longitudinally for the full length thereof; said camshaft having a plurality of cylindrical bearing portions the same diameter as said tubular support member cylindrical bearing surface and engaging therewith to form bearing means; said lubricating duct having lubricating passageway means for conducting lubricating oil from said lubricating duct to said bearing means.

7. The engine according to claim 6, including the interior surface of said cylinder head bores and the exterior surface of said tubular support member being cylindrical and of the same diameter; at least one valve associated with each of said cylinder heads and having actuating means driven by said camshaft; said tubular support member having a plurality of radially extending openings corresponding in number to and aligned with said valve actuating means; said camshaft having an integral abutment flange at one end axially abuting with said tubular member; said camshaft having a driving gear integrally secured to said abutment flange; screw means mounted on said cylinder heads and extending radially into corresponding bores in said tubular support member for securing said tubular support member against rotational movement.

8. The engine according to claim 1, wherein said tubular support member has an exterior cylindrical surface and an interior cylindrical surface eccentric with respect to said exterior cylindrical surface to provide wall portions of different thickness.

9. The engine according to claim 8, including a longitudinal extending lubricating duct within the wall portions of said tubular support member.

10. The engine according to claim 9, wherein said lubricating duct is located in the Wall portion having the largest wall thickness.

References Cited UNITED STATES PATENTS 870,065 11/ 1907 Welch 123-90 1,195,441 8/1916 Caron 123-59 1,235,110 7/1917 Coatalen 184-6 1,406,271 2/ 1922 Michelsen 123-90 1,514,066 11/1924 Page. 1,701,550 2/ 1929 Woolson 123-90 2,213,202 9/ 1940 Buchi 123-191 2,793,625 5/ 1957 Kolbe 123-195 X 2,865,341 12/1958 Dolza 123-195 X 3,022,775 2/1962 Bouvy 123-191 X 3,352,293 11/ 1967 Hulten 123-193 X FOREIGN PATENTS 305,017 7/1929 Great Britain. 403,300 12/1933 Great Britain.

AL LAWRENCE SMITH, Primary Examiner. 

